Make home page feature images clickable w/o links.

Closes #610 

![selected-databases-markup](https://cloud.githubusercontent.com/assets/96776/3786483/72d55e68-19d8-11e4-86c5-b8acb336f6a8.png)


![featured-images](https://cloud.githubusercontent.com/assets/96776/3786484/75f4d8d0-19d8-11e4-8058-aa2d47f1f533.gif)